The present invention relates to the field of polymer chemistry. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
There are numerous uses for organic polymers which are conductors of electricity at normal ambient temperatures. Potential application areas include organic conductors and semiconductors, elements in integrated electronic circuits, information storage systems, temperature sensors, gas and irradiation detectors, pressure indicators, rectifiers, and electrochromic display devices. Also, electrochemistry and photoelectrochemistry are potential areas of interest, particularly for battery and fuel cell applications. In addition, conducting polymers may be of use for static charge dissipation and electromagnetic interference shielding.
In many applications, it is desirable that an electrically conductive polymer be capable of dissolution in common solvents. Conductive polymers which are soluble in organic solvents such as acetone, methylene chloride, and benzene are known. However, prior to the present invention, there was no known electrically conductive organic polymer which is capable of dissolution in water. It is often preferable, where the application permits, to use water in connection with the manufacturing and processing of a conductive polymer, in order to avoid disadvantages involved in the use or organic solvents. These disadvantages include toxicity, cost of the solvent, and requirements of safe disposal of used solvent.
Liquid crystals are fluids that typically contain elongated organic molecules that spontaneously acquire long-range orientational order at characteristic temperatures or concentrations. Lyotropic liquid crystalline polymers are a type of liquid crystal polymers that form ordered fluid phases in solution. Liquid crystalline polymers have technological potential in areas ranging from microelectronics to biotechnology. Polymers having liquid crystal properties are unusually strong and tough; for example, a liquid crystalline polymer is the principal material used in "bullet-proof" vests.
The starting point for synthesis of polymers of the present invention is a five-member ring consisting of four carbon atoms and a sulfur atom (thiophene) or a nitrogen atom (pyrrole). Polythiophene and polypyrrole, the polymers derived from these monomers, are not soluble in any common solvent and are not electrically conductive unless a dopant is added. However, poly(3-alkylthiophene), which requires a dopant for electrical conductivity, is soluble in common organic solvents if the alkyl group is comprised of four or more carbons, as discussed in a brief article by Jen et al. entitled "Highly Conducting, Soluble, and Environmentally stable Poly(3-alkyl-thiophene)," J. Chem. Soc. Comm., 1346 (1986).
A. O. Patil et al., "Water-Soluble Conducting Polymers," J. Am. Chem. Soc. 109, 1858 (Mar. 18, 1987) reports on two water-soluble conducting polymers: sodium poly(3-thiophene-.beta.-ethylsulfonate) and sodium poly(3-thiophene-.delta.-butanesulfonate).